Unclassified Summary of Information Handling and Sharing Prior to the April 15, 2013 Boston Marathon Bombings - https://oig.justice.gov/reports/2014/s1404.pdf
"A decade earlier, Tamerlan and Dzhokhar Tsarnaev immigrated to the United States from Kyrgyzstan with their parents Anzor Tsarnaev and Zubeidat Tsarnaeva. Anzor Tsarnaev, an ethnic Chechen, his wife Zubeidat Tsarnaeva, and their son Dzhokhar Tsarnaev arrived in the United States from Kyrgyzstan in 2002. They applied for and received an immigration benefit. The elder son, Tamerlan Tsarnaev, and his sisters, Bella and Ailina Tsarnaeva, arrived in the United States in 2003 and also received an immigration benefit. In the years that followed, all six family members became Lawful Permanent Residents of the United States."
"In March 2011, the FBI received information from the FSB alleging that Tamerlan Tsarnaev and Zubeidat Tsarnaeva were adherents of radical Islam and that Tamerlan Tsarnaev was preparing to travel to Russia to join unspecified underground groups in Dagestan and Chechnya. The FBI-led Joint Terrorism Task Force in Boston (Boston JTTF) conducted an assessment of Tamerlan Tsarnaev to determine whether he posed a threat to national security and closed the assessment three months later having found no link or “nexus” to terrorism."
"In September 2011, the FSB provided the Central Intelligence Agency (CIA) information on Tamerlan Tsarnaev that was substantively identical to the information the FSB had provided to the FBI in March 2011. In October 2011, the CIA provided information obtained from the FSB to the the National Counterterrorism Center (NCTC) for watchlisting purposes, and to the FBI, Department of Homeland Security (DHS), and the Department of State for their information. Upon NCTC’s receipt of the information, Tamerlan Tsarnaev was added to the terrorist watchlist."